It is known to suspend from the top of a structure around which wire is to be wound a mobile unit capable of holding a supply of wire in such a manner that said wire may be drawn therefrom, the unit being appropriately positioned and supported in relation to any selected circumferential trough or channel in or on the surface of the structure around which the wire is to be wound, so that, when the unit is carried around the structure at a desired speed and with one end of the wire securely anchored in the selected trough or channel, the wire will be wound around the structure.
In our prior U.S. Pat. No. 3,404,497 we have described a concrete pressure vessel or other concrete structure which is circumferentially stressed by means of prestressing wire or strands wound therearound under tension in a plurality of layers, such wire or strands being accommodated in circumferential troughs or channels which are provided in or on the outer surface of the vessel and serve to locate the layers of wire.